In March of 1974, the Grateful Dead unveiled a sound system unlike any that had ever been, or that the world has seen (heard) since. It was designed by audio engineer Owlsley “Bear” Stanley, who had recently been released from prison, and at the time was the largest portable (somewhat) PA ever. The main component of the system was a huge wall of speakers erected upstage, behind the band. This mountain of speakers became known as the “wall of sound”. The system was unique due to its size, (it is reported as consisting of around 600 speakers, weighing 75 tons, and requiring 26,000-28,000 watts of continuous power, depending on the current point in its evolution) as well as its functionality and quality.

The system was actually six individual PA systems operating independently but together. There was a separate system for vocals, lead guitar, rhythm guitar, bass, drums, and piano. Each had its own set of amps, processing, and speakers. Band members had control of the area of the wall that was providing reinforcement for their particular instrument, as well as the levels of their vocals. A main (or monitor) mixing console was not required for the operation of “the wall”.

The challenges associated with such a set-up are obvious, the least of which not being the requirements for transportation and installation of this behemoth. The time it took to load in made it necessary for the band to tour with three complete packages and leapfrog much in the way that a broadway show would send gear in advance. There were over 20 crew members responsible for putting it all together, with assistance from local labor (much of which was provided by members of the Hell’s Angels motorcycle club, which added an interesting dynamic).

This was actually the band’s second attempt at creating such a complex audio arrangement. The first experiment came about a year earlier and was met with tragic results. Every tweeter blew as the band began their first number.

The installation process would begin with the construction of a large scaffolding rig on the downstage side of where the speaker wall was to be erected. As the wall grew, block-and-falls were employed to hoist speakers, which were essentially wooden boxes affixed with speaker cones, up to the higher levels. The speakers were tied to the hoists with rope, raised up and landed on top of the last level. There were also chain motors that were used to lift some of the more obnoxiously massive parts, such as the cylindrically shaped structure of cones that was the section of the wall which provided reinforcement of high and mid-range vocals.

I imagine this was probably some of the oddest seeming stage work to ever take place. A bunch of gangsters building something equivalent to the pyramids while dogs and small children run around on stage. There was even some occasional breast-feeding.

Conventionally, main speaker arrays are located in the downstage corners of the stage, either flown or ground-based. Monitors are used to direct sound back towards the band but, although configured to the performers’ preferences, it sounds nothing like what the audience is hearing. The upstage location of the wall allows the band to hear exactly the same thing that the audience hears, but it also makes the avoidance of feedback somewhat tricky.

What happens, typically, is sound enters a microphone, is amplified and pushed out a speaker, goes back into the mic and this loop pattern creates some of the most awful noise known to human ears. Several steps were needed to prevent this phenomenon from ruining the effectiveness of the whole system.

First of all, the gargantuan cylindrical structure which brought the higher end of the vocals was placed at the top. It produced more horizontal than verticle dispersion, so they could keep most of the sound out of the mics. The low end speakers were arranged in columns lower in the wall and were less likely to cause feedback. Regardless of the physical separation of all the speakers in the vocal system, it was designed in a way to allow all frequencies to be heard equally well. That’s what they say.

In addition to just putting the speakers up high, more technical efforts were needed in order to further minimize the presence of feedback. The vocal mics were actually matched pairs of condenser mics run “out of phase”. The mics were arranged one on top of the other a few inches apart. (60 mm, actually. Not sure if that matters). The band members would sing into the top one, and the sound from this would be amplified like normal. The mics in reverse phase would combine signals in a “differential summing amp” (don’t ask) and cause all sound common to both mics to cancel each other out, thus eliminating feedback from the overall mix. That was hard.

The parts of the system associated with the instruments were slightly less complicated. Each had its own system of amps and crossovers, which would send different frequncies to different parts of the wall, but one of the more interesting aspects of the instrumental amplification was how Phil Lesh’s bass was integrated into the system.

The bass was reproduced quadrophonicaly, which is like stereo times two. Instead of just a left and a right there were actually 4 sound “areas”. Coincidentaly, there are four strings on the bass. It was configured so that each string was on its own channel, and the signal from each was bussed through its own system of amplification and projected from its own group of speakers. Each string came out of a different place in the wall.

The kick drum used its own amplification channel and a column of sixteen 15 inch speakers. That’s sixteen 15 inch speakers, all kick drum. It doesn’t necessarily mean it’s loud, although it can be. It was more about having head room. If all the speakers aren’t being pushed to their capacity the resulting sound is going to be much cleaner.

Amplification of all the instruments and vocals was acheived in a manner in which each speaker was dedicated to a small portion of the entire sound output.
This resulted in an impeccably clean sound, almost entirely free of intermodulation distortion. In conventional speaker arrangements, sounds of different qualities and frequencies compete with each other as they cause speaker cones to behave differently than if they were just producing one type of sound. So a sound system could produce as much volume as this one with the use of much less power, but it would be inferior in overall quality and lack the ability to retain clarity in distances of up to a half mile, or be as cool, as this one.

The wall of sound can be seen in the documentary/concert film The Greatful Dead Movie. It was filmed during a 5 night run at San Francisco’s Winterland Ballroom and contains concert footage as well as accounts of the technical aspects of the Dead’s live performance. It’s the third greatest rock and roll movie of all time, right behind “This Is Spinal Tap” and The Band’s The Last Waltz, which, perhaps not coincidentaly, was also filmed at Winterland.

There is a production credit for IA 16 which rolls by as time lapse footage reveals the deconstruction of the scaff. (Man those guys are fast). I wouldn’t assume that too many of the Hell’s Angels are cardholders, but there’s some representation happening. Probably working under a CBA.

This sit-down in San Francisco marked the end of the road, litteraly, for this mighty wall. The rising costs of fuel and logistical headaches forced the band to abandon this expirement after about 50 shows in six months. It also turned out that the Angels didn’t exactly create a peaceful work environment. These factors also led the band to decide to “retire” themselves. They only played a handful of shows in 1975 and didn’t really start touring again, with a more conventional sound system from here on out, until the middle of 1976. The band would remain whole (relatively) for another twenty years until all the things caught up with Jerry in 1995. (Crying a little right now).

A lot of this might seem pretty complicated, but remember, it was really just some dudes (and one chic) smoking a bunch of weed and screwing around every night.